A dental glass ionomer cement is a dental cement having many characteristics such that it has superior biocompatibility and adhesive strength and excellent esthetics and that it can be expected to have a caries preventing effect by fluorine contained in the glass powder. By utilizing many of these characteristics, the dental glass ionomer cement is used for wide applications in the dental field, such as filling of a caries cavity, cementing of a crown, an inlay, a bridge, or an orthodontic bracket or band, lining of a cavity, core build up, pit and fissure sealing, and adhering at the time of filling a dental composite resin.
However, the dental glass ionomer cement involves such a defect that if it comes into contact with a water such as saliva at the initial stage of setting, the setting reaction is inhibited, whereby the final physical properties are decreased. This is caused by the fact that since a acid-base reaction between a polycarboxylic acid (acid) and a fluoroaluminosilicate glass (base) in the dental glass ionomer cement is carried out in the presence of water, the dental glass ionomer cement is liable to be influenced by the water. And, there is generated a phenomenon in which a surface which has come into contact with the water at the initial stage of setting becomes brittle, and the cement becomes chalky, whereby the esthetics are spoiled. With respect to this issue, there have, hitherto been tried many improvements. There are laid open technologies for making the setting time, such as, for example, addition of a chelating agent in Japanese Patent Publication No. 54-21858; addition of a fluorocomplex salt in Japanese Patent Laid-Open No. 57-2210; and addition of a polymerizable unsaturated organic compound and a polymerization catalyst to the liquid component in Japanese Patent Laid-Open No. 6-27047. In addition, the present inventor has proposed a technology utilizing a redox reaction by addition of an oxidation-reduction catalyst in which the setting reaction takes place even without irradiation with a visible light in Japanese Patent Laid-Open No. 8-26925. By using these proposed dental glass ionomer cement, the problems which occur due to the contact with a water at the initial stage of setting, such as brittleness and disintegration, can be overcome, the manipulability is greatly improved by the photocuring, and the physical properties such as adhesive strength to a tooth, bending strength, and transparency are improved.
On the other hand, as a defect of the dental glass ionomer cement, it is pointed out that in case of using it for filling, the polished surface after setting is rough, and the film thickness is thick.
In other words, due to the fact that the smoothness of the polished surface of a restoration is insufficient, there is an inconvenience that in the oral cavity, it is rough and unpleasant, whereby a patient is liable to complain of a feeling of physical disorder. In case of using it for filling of anterior teeth in particular, there is generated a phenomenon that the esthetics are somewhat inferior, and since the film thickness is thick, in case of using it for cementing of a crown or an inlay, the prosthesis is liable to come up and a fittness becomes worse. Actually, when the dental glass ionomer was compared with the dental composite resin and dental resin cement, with respect to the ten-point average surface roughness immediately after the setting, the dental composite resin showed about 3.0 .mu.m, whereas the dental glass ionomer cement showed a large value as about 8.0 .mu.m; and with respect to the film thickness, the dental resin cement exhibited about 5.about.10 .mu.m, whereas the dental glass ionomer cement exhibited a large value as about 15.about.20 .mu.m.
As described above, the improvements in the dental glass ionomer cement have hitherto been focused only on the improvements in the physical properties or manipulability.